Around the time of Oracle’s acquisition of Sun and hence MySQL, there was a lot of discussion as to whether MySQL’s GPL license could inhibit MySQL storage engine vendors from selling their products without MySQL code (e.g., with MySQL-fork front-ends). I argued No. Most people, however, seemed to think “Yes, and even if the matter isn’t clear, the threat of nasty lawyers creates enough FUD to be a practical market problem for the storage engine vendors.” Based on those concerns, I eventually took the position that Oracle should be inhibited for antitrust reasons from invoking its real or alleged GPL rights to mess with the MySQL storage engine vendors. Oracle’s agreement with the EU alleviated that concern, except that there was an annoying time limit on the alleviation.
Now a related can of worms has been opened in a related technology area — WordPress and WordPress themes. Since many bloggers use WordPress, this has gotten a lot of attention, and some interesting new insights have emerged.
Um, in case you didn’t know: WordPress is the software that runs blogs such as this, and it’s a GPLed open source project. However, the user interface — look, feel, and behavior alike — are determined by separate themes, that one usually gets from third parties (WordPress ships with a a few default choices).
It started when Matt Mullenweg went after the makers of an unfree theme Thesis, and wielding a legal opinion from the Software Freedom Law Center. The gist of the SFLC’s argument seems to be
They are derivative of WordPress because every part of them is determined by the content of the WordPress functions they call. As works of authorship, they are designed only to be combined with WordPress into a larger work.
And of course the point of the GPL is that if you create a derivative work of something GPLed, you have to GPL it yourself.
However, Perpetual Beta pointed out that, under the rules of copyright law as expressed in a court case known as Galoob, depending on another program does not make something a derivative work. This is actually blindingly obvious, as in the example of any program that runs on top of an operating system. Or for more examples see Dave Winer on the point.
Perpetual Beta further argued that, even if it were a derivative work, fair use would let one copy it anyway. I.e., if you’re engaging in “fair use,” you’re entitled to do what otherwise would be a copyright violation. Good point. The GPL license says in effect “You only are allowed to use this material (in certain ways) if you do as we say about your own work,” so that is defeated if the Fair Use Doctrine lets you say “Um, actually, I’m using this without your permission, so buzz off.”
GPL advocates can pontificate all they want about certain uses of GPLed code violating their license terms. But if either of these arguments holds up — and it looks to me like both do — a program that invokes GPLed code is not subject to the GPL just based on those invocations. And that, in turn, would more than imply that MySQL storage engine vendors could use GPLed MySQL-compatible front-ends without being under any GPL obligation themselves.